Infrared thermal radiation light source has important applications value in such fields as photoacoustic spectroscopy detection, and its light distribution characteristic is the basis of subsequent optical system design. In this paper, according to the variation law of radiant flux of the infrared thermal radiation light source under water cooling, a method for quickly obtaining the light distribution characteristic of a high-power infrared thermal radiation light source is proposed and verified. The experimental results show that the radiant flux of the light source is at an angle of 80°, and the radiant flux on both sides decreases slowly, and the energy is dispersed in the range of 0°--130°, 54.5% of which is concentrated in the range of 50°--110°. Furthermore, the accuracy and effectiveness of the rapid measurement method are verified through a comparative experiment of the light distribution characteristics under stable radiation for a long time. Beyond that, breaking the limit of light source angle in the ZEMAX software, the measured data is used to build a model and simulate the experimental process for verification. In conclusion, in the absence of the light distribution curve of the high-power infrared thermal radiation source, the proposed method can obtain the light distribution characteristics simply and quickly, providing initial conditions for optical design.